DIYbanter - View Single Post - power supply "sticks" in current limiting mode

mike[_22_]

On 4/17/2014 1:44 PM, wrote:
Actually I didn't want to pontificate but I was going to say that it looks like someone studied instrumentation

design but forgot basic circuit design. Someone should tell him that
more components don't make the design better.

I think using the upside down design as you put it results in a bit better stability, that is if you know

how to do it.
Not sure that's true.
I'd bet that someone did it because they had NPN transistors and didn't
know any better. Then that design got stolen and "improved" by some
competitor...repeat
a few times...add digital readouts...and this is what you get.
This does not look at all like a design.
Looks like a bad start that kept getting patched instead of fixing the
design.

If the thing can't foldback lower than 340mA, they didn't know how to do
it. In that state you

couldn't test a 12 volt 1 watt Zener.
It's not foldback.
There are pots galore. You can set the low limit below 340 ma, but mine
latches up if you do.

If the design is anything at all like the one posted, I don't see any quick fixes. I could probably redesign

it faster. Maybe you should guve that a go. You have a transformer and a
box, and apparently two readouts.

snip

s like you could keep their power transistors and big resistors, take a
coupe of your own OP AMPs and make it into something useful.

If I wanted another analog supply, I've got a design I did over 40 years
ago that works fine.
As you probably know, the schematic is trivial.
The "art" needed for proper operation is a scarce commodity.
I've fixed many "production-ready" designs by experienced engineers.
What shows up as an element on the schematic is only a part of what's
important.

Then, there are issues with making the meters autorange and the relays
that switch the transformer...and the circuit board and and and and...
It's all a royal pain in the ass.

I don't need another power supply or another project.

In the meantime you might want to repost, or I think they call it "top post" this so everyone sees it.

SOmeone might have an idea who uses Thunderbird or something to get
here. Alot of the oldtimers do.